We all know our scheduling availability, and you need to be candid about how many hours per week you can truly commit to the role.
If you are available 40+ hours a week, that is great! Share this with the interviewer, and share if there are any times of the week that you would not be available to work extra hours.
If you are not able to work overtime, you need to share this with the interviewer. If there are certain times of the year when you could work overtime, be sure to share this information with the interviewer as well clearly explaining what additional hours or days of the week you could be available.